The present invention generally relates to a structure of a speech path for a switching system. More particularly, the invention is concerned with a speech path structure which is profitably suited for the speech path system of a so-called ATM (Asynchronous Transfer Mode) switching system adapted for switching or exchanging information for communication on a time-division/multiplex basis by using packets each of a fixed length.
As a typical one of the speech paths used heretofore for the switching systems, there can be mentioned a digital time division speech path which is suited for a line switching system and which is composed of a speech path memory, a control memory and a space division switch.
The switch is equipped with a controller for writing switching information in the control memory, wherein time divided and multiplexed information makes access to the control memory at every multiplexed unit (time slot) to derive information concerning the destination or addresses to which the information is to be sent, whereon the connection is established through the switch in accordance with the information as read out.
Although the time division speech path system is suited for the line or call switching, it can not always be said that this system is suited for communications of different rates for which demand is expected to increase in the future. Further, the digital time division speech path is not necessarily suited as multi-media having a variety of properties. On the other hand, a packet switching system which seems capable of coping with more flexibly the requirements mentioned above encounters difficulty in application to the communications of different rates and among others a high-speed broad band communication at the present state of the art.
Under the circumstances, study and development of the ATM (Asynchronous Transfer Mode) system are in progress as a novel switching system. The ATM system is characterized in that all information inclusive of communication information, call processing information and others is handled in terms of packets referred to as the cells as the unit of information to be processed. In realizing the ATM switching system, it is of course important to solve a problem in what structure the speech path is to be realized for practical applications. So far as the switch function is concerned, several proposals have already been made. However, there remain unsolved problems concerning other functions required for the ATM speech path system such as, for example, cell phase synchronizing function, label conversion, cell flow control and other functions. In other words, it is a matter of primary concern to solve the problem how to implement the abovementioned functions in order to structurize a realistic speech path system.
Reference is hereby made to the following copending applications dealing with related subject matter and assigned to the assignee of the present application: 1. "Time-Division Channel Arrangement" by Yoshito Sakurai et al, assigned U.S. Ser. No. 96,011, and 2. "Switching System And Method Of Construction Thereof" by Yoshito Sakurai et al, assigned U.S. Ser. No. 218,217.
Further, as the related arts, the following patents may be mentioned:
U.S.P. 4,594,708 PA1 U.S.P. 4,603,416 PA1 U.S.P. 4,782,478 PA1 U.S.P. 4,813,037